Events sent to clients are queued in a buffer and written to the socket later - typically when the compositor has handled all requests and goes back to block in the event loop. This function flushes all queued up events for a client immediately.

The function pointed by iterator will be called for each resource owned by the client. The user_data will be passed as the second argument of the iterator function. If the iterator function returns WL_ITERATOR_CONTINUE the iteration will continue, if it returns WL_ITERATOR_STOP it will stop.

Creating and destroying resources while iterating is safe, but new resources may or may not be picked up by the iterator.

This function returns the process ID, the user ID and the group ID for the given client. The credentials come from getsockopt() with SO_PEERCRED, on the client socket fd. All the pointers can be NULL, if the caller is not interested in a particular ID.

Be aware that for clients that a compositor forks and execs and then connects using socketpair(), this function will return the credentials for the compositor. The credentials for the socketpair are set at creation time in the compositor.

Be sure to use the file descriptor from the client for inspection only. If the caller does anything to the file descriptor that changes its state, it will likely cause problems.

See also wl_client_get_credentials(). It is recommended that you evaluate whether wl_client_get_credentials() can be applied to your use case instead of this function.

If you would like to distinguish just between the client and the compositor itself from the client's request, it can be done by getting the client credentials and by checking the PID of the client and the compositor's PID. Regarding the case in which the socketpair() is being used, you need to be careful. Please note the documentation for wl_client_get_credentials().

This function can be used for a compositor to validate a request from a client if there are additional information provided from the client's file descriptor. For instance, suppose you can get the security contexts from the client's file descriptor. The compositor can validate the client's request with the contexts and make a decision whether it permits or deny it.